Duskfog

The duskfog can move through other creatures and objects as if they were Difficult Terrain. It takes 5 (1d10) Force damage if it ends its turn inside an object.

Constitution Saving Throw: DC 14, one creature the duskfog can see within 5 feet. Failure: 18 (4d8) Necrotic damage and the duskfog regains Hit Points equal to the Necrotic damage dealt.